4,616 research outputs found
XMM-Newton observations of IGRJ18410-0535: The ingestion of a clump by a supergiant fast X-ray transient
IGRJ18410-0535 is a supergiant fast X-ray transients. This subclass of
supergiant X-ray binaries typically undergoes few- hour-long outbursts reaching
luminosities of 10^(36)-10^(37) erg/s, the occurrence of which has been
ascribed to the combined effect of the intense magnetic field and rotation of
the compact object hosted in them and/or the presence of dense structures
("clumps") in the wind of their supergiant companion. IGR J18410-0535 was
observed for 45 ks by XMM-Newton as part of a program designed to study the
quiescent emission of supergiant fast X-ray transients and clarify the origin
of their peculiar X-ray variability. We carried out an in-depth spectral and
timing analysis of these XMM-Newton data. IGR J18410-0535 underwent a bright
X-ray flare that started about 5 ks after the beginning of the observation and
lasted for \sim15 ks. Thanks to the capabilities of the instruments on-board
XMM-Newton, the whole event could be followed in great detail. The results of
our analysis provide strong convincing evidence that the flare was produced by
the accretion of matter from a massive clump onto the compact object hosted in
this system. By assuming that the clump is spherical and moves at the same
velocity as the homogeneous stellar wind, we estimate a mass and radius of Mcl
\simeq1.4\times10^(22) g and Rcl \simeq8\times10^(11) cm. These are in
qualitative agreement with values expected from theoretical calculations. We
found no evidence of pulsations at \sim4.7 s after investigating coherent
modulations in the range 3.5 ms-100 s. A reanalysis of the archival ASCA and
Swift data of IGR J18410-0535, for which these pulsations were previously
detected, revealed that they were likely to be due to a statistical fluctuation
and an instrumental effect, respectively.Comment: Accepted for publication on A&A. V2: Inserted correct version of
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Elastic pp Scattering at LHC Energies
We consider the first LHC data for elastic pp scattering in the framework of
Regge theory with multiple Pomeron exchanges. The simplest eikonal approach
allows one to describe differential elastic cross sections at LHC, as well as
pp and scattering at lower collider energies, on a reasonable level.Comment: 11 pages, 5 figures, and 1 tabl
Longevity risk and economic growth in sub-populations: evidence from Italy
Forecasting mortality is still a big challenge for Governments that are interested in reliable projections for defining their economic policy at local and national level. The accuracy of mortality forecasting is considered an important issue for longevity risk management. In the literature, many authors have analyzed the long-run relationship between mortality evolution and socioeconomic variables, such as economic growth, unemployment rate or educational level. This paper investigates the existence of a link between mortality and real gross domestic product per capita (GDPPC) over time in the Italian regions. Empirical evidence shows the presence of a relationship between mortality and the level of real GDPPC (and not its trend). Therefore, we propose a multi-population model including the level of real GDPPC and we compare it with the Boonen–Li model (Boonen and Li in Demography 54:1921–1946, 2017). The validity of the model is tested in the out-of-sample forecasting experiment
On the impact of agents with influenced opinions in the swarm social behavior
We consider a simplified version of the Taylor model, typically used in the collective dynamics of continuous exchange of opinions, to describe the properties of swarm formation in the presence of external sources of influence or prejudices affecting a number of agents in the network. Such external sources are responsible for the breakdown of the consensus equilibrium and directly influence certain other individuals in the network, which we denote as quasi-stubborn agents. These quasi-stubborn agents participate in consensus with other individuals, but are able to indirectly influence the opinions of the entire system. In particular, we show that the swarm in steady-state moves towards the convex hull of the opinions of the quasi-stubborn agents. This is an interesting result that allows a more accurate estimation of the final opinions in a social network. In the case of two prejudiced agents, an explicit expression of the stationary opinions is provided in terms of the Moore-Penrose inverse of the Laplacian of the graph. Numerical simulations are presented to illustrate the properties of the considered model
XMM-Newton and Swift observations of XTE J1743-363
XTEJ1743-363 is a poorly known hard X-ray transient, that displays short and
intense flares similar to those observed from Supergiant Fast X-ray Transients.
The probable optical counterpart shows spectral properties similar to those of
an M8 III giant, thus suggesting that XTEJ1743-363 belongs to the class of the
Symbiotic X-ray Binaries. In this paper we report on the first dedicated
monitoring campaign of the source in the soft X-ray range with XMM-Newton and
Swift/XRT. T hese observations confirmed the association of XTEJ1743-363 with
the previously suggested M8 III giant and the classification of the source as a
member of the Symbiotic X-ray binaries. In the soft X-ray domain, XTEJ1743-363
displays a high absorption (~6x10^22 cm^-2 ) and variability on time scales of
hundreds to few thousand seconds, typical of wind accreting systems. A
relatively faint flare (peak X-ray flux 3x10^-11 erg/cm^2/s) lasting ~4 ks is
recorded during the XMM-Newton observation and interpreted in terms of the wind
accretion scenario.Comment: Accepted for publication on A&
The supergiant fast X-ray transients XTE J1739-302 and IGR J08408-4503 in quiescence with XMM-Newton
Context. Supergiant fast X-ray transients are a subclass of high mass X-ray
binaries that host a neutron star accreting mass from the wind of its OB
supergiant companion. They are characterized by an extremely pronounced and
rapid variability in X-rays, which still lacks an unambiguous interpretation. A
number of deep pointed observations with XMM-Newton have been carried out to
study the quiescent emission of these sources and gain insight into the
mechanism that causes their X-ray variability. Aims. We continued this study by
using three XMM-Newton observations of the two supergiant fast X-ray transient
prototypes XTEJ1739-302 and IGR J08408-4503 in quiescence. Methods. An in-depth
timing and spectral analysis of these data have been carried out. Results. We
found that the quiescent emission of these sources is characterized by both
complex timing and spectral variability, with multiple small flares occurring
sporadically after periods of lower X-ray emission. Some evidence is found in
the XMM-Newton spectra of a soft component below ~2 keV, similar to that
observed in the two supergiant fast X-ray transients AXJ1845.0-0433 and
IGRJ16207-5129 and in many other high mass X-ray binaries. Conclusions.We
suggest some possible interpretations of the timing and spectral properties of
the quiescent emission of XTEJ1739- 302 and IGR J08408-4503 in the context of
the different theoretical models proposed to interpret the behavior of the
supergiant fast X-ray transients.Comment: 13 pages, 14 figures. Accepted for publication in A&A. V2: Corrected
few typo
The supergiant fast X-ray transient IGRJ18483-0311 in quiescence: XMM-Newton, Swift, and Chandra observations
IGR J18483-0311 was discovered with INTEGRAL in 2003 and later classified as
a supergiant fast X-ray transient. It was observed in outburst many times, but
its quiescent state is still poorly known. Here we present the results of
XMM-Newton, Swift, and Chandra observations of IGRJ18483-0311. These data
improved the X-ray position of the source, and provided new information on the
timing and spectral properties of IGR J18483-0311 in quiescence. We report the
detection of pulsations in the quiescent X-ray emission of this source, and
give for the first time a measurement of the spin-period derivative of this
source. In IGRJ18483-0311 the measured spin-period derivative of
-(1.3+-0.3)x10^(-9) s/s likely results from light travel time effects in the
binary. We compare the most recent observational results of IGRJ18483-0311 and
SAXJ1818.6-1703, the two supergiant fast X-ray transients for which a similar
orbital period has been measured.Comment: Accepted for publication in MNRA
IGRJ16479-4514: the first eclipsing supergiant fast X-ray transient?
Supergiant fast X-ray transients are a new class of high mass X-ray binaries
recently discovered with INTEGRAL. Hours long outbursts from these sources have
been observed on numerous occasions at luminosities of ~1E36-1E37 erg/s,
whereas their low level activity at ~1E32-1E34 erg/s has not been deeply
investigated yet due to the paucity of long pointed observations with high
sensitivity X-ray telescopes. Here we report on the first long (~32 ks) pointed
XMM-Newton observation of IGR J16479-4514, a member of this new class. This
observation was carried out in March 2008, shortly after an outburst from this
source, with the main goal of investigating its low level emission and physical
mechanisms that drive the source activity. Results from the timing, spectral
and spatial analysis of the EPIC-PN XMM-Newton observation show that the X-ray
source IGRJ16479-4514 underwent an episode of sudden obscuration, possibly an
X-ray eclipse by the supergiant companion. We also found evidence for a soft
X-ray extended halo around the source that is most readily interpreted as due
to scattering by dust along the line of sight to IGRJ16479-4514. We discuss
this result in the context of the gated accretion scenarios that have been
proposed to interpret the behaviour of supergiant fast X-ray transient.Comment: Accepted for publication in MNRAS letter. 6 pages and 5 figures. We
updated one reference and the acknowledgment
Atwood’s Machine and Electromagnetic Induction: A Real Quantitative Experiment to Analyze Students’ Ways of Reasoning
We report a research-based proposal on electromagnetic induction within the theoretical framework of the Model of Educational Reconstruction. The proposal is based on a sequence of inquiry-based experimental activities centered on hands-on materials and Real-Time quantitative experiments, through which students explore the phenomenology of electromagnetic induction. The sequence was planned to address Faraday-Neumann-Lenz law analyzing the involved physics quantities and constructing quantitative relationships between them. Our hypothesis was based on the idea that phenomenological explorations performed through online sensors promote a functional understanding of electromagnetic induction and help students to face the conceptual knots highlighted by international literature about these phenomena.The educational sequence was proposed to a sample of 87 high school students with the aim of analyzing the evolution of the educational processes employing a set of inquiry-based tutorials. The qualitative analysis of students’ answers demonstrates that students increased their knowledges in the analysis of electromagnetic induction phenomena recognizing the fundamental role of time-variation of the magnetic field flux in the Faraday-Neumann-Lenz la
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